Detector detecting transmission performance of optical composite cable

ABSTRACT

The detector comprises a loopback unit  10  which is connected to a connector formed at one end of an optical camera cable, an optical loop fiber  11  connecting a first optical fiber  31  and a second optical fiber  32 , and a short-circuit wiring  12  which short-circuits plural electric lines of the optical camera cable. The detector also comprises a measuring unit  40  comprising a transmission loss measuring part which is connected to a connector formed at the other end of the optical camera cable and measures transmission loss between the first optical fiber and the second optical fiber, a resistivity measuring part which measures resistivity between electric lines, a disconnection detecting part which detects connection or disconnection of electric lines by using measured resistivity, and a display part, which displays the result of transmission loss measured by the transmission loss measuring part and connection or disconnection detected by the disconnection detecting part.

This is a patent application based on a Japanese patent application No.2005-86710 which was filed on Mar. 24, 2005, and which is incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a device which detects transmissionstatus of an optical composite cable comprising optical fibers andelectric lines. Mainly, the present invention relates to a devicedetecting disconnection and transmission loss of an optical fiber.

BACKGROUND ART

Conventionally, as shown in a patent document 1, i.e., Japanese PatentApplication Laid-open No. 2000-59661, an optical composite cable for aTV camera which comprises a pair of optical fibers, a pair of signallines, and a shield line, is a common and well-known example in order tocontrol a TV camera. Image data and sound signals of a TV camera aretransferred through optical fibers, control signals controlling thecamera are transferred through signal lines, and electric power issupplied to the TV camera through power supply lines. This opticalcomposite cable is used in the open air.

For example, in order to broadcast a golf game, it has been necessary toinstall cameras at a lot of spots of the course and to connect thosecameras and a relay car by using a large number of conventional opticalcomposite cables.

DISCLOSURE OF THE INVENTION

Problems to be Solved

In order to install optical composite cables outdoor, however, problemspersist in disconnection of optical fibers and electric lines andincreasing transmission loss owing to contamination of soiled connectionends of optical fibers and deterioration of the optical fibers and soon. So it has been necessary to connect a TV camera to the connectionend of the optical composite cable to be installed from the relay carbefore broadcasting the game on TV to monitor operation and imagequality of the camera. After checking one optical composite cable, thenext optical composite cable is extended and then the TV camera has tobe connected to the end of the extended cable to monitor the quality ofthe transmitted image. Accordingly, they need to move a heavy TV camerafrom one connection end of the optical composite cable to the other, andthat bothers to check operation of each optical composite cable to beinstalled.

In order to solve the above-described problems, the present inventionaims to detect transmission characteristic and transmission status suchas disconnection of the optical composite cable more easily.

That is, a first aspect of the present invention is a detector detectingtransmission performance of optical composite cable which comprisesoptical fibers and electric lines, comprising: a first unit, which isconnected to a connector formed at one end of the optical compositecable and comprises a optical loop part connecting a first optical fiberand a second optical fiber and a short-circuit part which short-circuitsplural electric lines in the optical composite cable; and a second unitcomprising a transmission loss measuring part, which is connected to aconnector formed at the other end of the optical composite cable andmeasures transmission loss between ends of the first optical fiber andthe second optical fiber returned by the optical loop unit, aresistivity measuring part, which measures resistivity between ends ofelectric lines returned by the short-circuit part, a disconnectiondetecting part, which detects connection or disconnection of electriclines by using measured resistivity, and a display part, which displaysthe result of transmission loss measured by the transmission lossmeasuring part and connection or disconnection detected by thedisconnection detecting part.

Here, numbers of the optical fibers and the electric lines constructingthe optical composite cable may not be limited. Generally, the opticalcomposite cable comprises a pair of optical fibers, a pair of electricsignal lines (hereinafter simply referred to as signal lines), and apair of electric power supply lines (hereinafter simply referred to aspower supply lines). The electric line comprises a pair of electricsignal lines and a pair of electric power supply lines. The first unitreturns optical signal and electric signal transmitted from the secondunit. The second unit transmits optical signal and electric signal,measures transmission loss between ends of returned optical fibers(hereinafter referred to as transmission loss between ends of opticalfibers) and resistivity between ends of electric lines which areshort-circuited at one end (hereinafter referred to as resistivitybetween ends of electric lines), and displays quantity of transmissionloss and status of disconnection or trouble according to thosemeasurement results.

A second aspect of the present invention is that the electric linescomprise a pair of signal lines and a pair of power supply lines and ashield line, the resistivity measuring part measures resistivity betweenends of a pair of signal lines returned from the short-circuit part,resistivity between ends of a pair of power supply lines returned fromthe short-circuit part, and each resistivity between each ends of eachsignal line and a shield line returned from the short-circuit part, eachresistivity between each end of each power supply line and the shieldline returned from the short-circuit part, and the disconnectiondetecting part detects each disconnection status of the signal line, theelectric line, and the shield line according to those measurementresults.

When there are 5 electric lines, resistivities 6 in total are measured.The resistivities are: resistivity between ends of the signal linesreturned from the first unit (hereinafter referred to as resistivitybetween ends of signal lines), resistivity between ends of the powersupply lines returned from the first unit (hereinafter referred to asresistivity between ends of power supply lines), each resistivitybetween ends of each signal line and the shield line connected by thefirst unit (hereinafter referred to as resistivity between end of signalline and shield line), and each resistivity between ends of each powersupply line and the shield line connected by the first unit (hereinafterreferred to as resistivity between ends of power supply line and shieldline). When resistivity between end of signal lines is larger than thepredetermined value, the signal lines are judged to be disconnected.When resistivity between ends of power supply lines is larger than thepredetermined value, the power supply lines are judged to bedisconnected. Under condition that the power supply lines are normal,resistivity of the shield line is half a value of sum of two resistivityvalues between ends of each power supply lines and the shield linesubtracted by resistivity value between ends of the power supply lines.When the power supply lines are broken and the signal lines are normal,resistivity of the shield line is half a value of sum of two resistivityvalues between ends of each signal line and the shield line subtractedby resistivity value between ends of the signal lines.

A third aspect of the present invention is that the transmission lossmeasuring part outputs a pulse optical signal to the first optical fiberand receives the pulse optical signal from the second optical fibersynchronizing with sending said pulse optical signal.

Outputting the optical signal as a pulse enables to save electric powerconsumption of the second unit.

Through employment of the aforementioned aspects of the presentinvention, the aforementioned drawbacks can be overcome effectively andrationally.

EFFECT OF THE INVENTION

Effects to be obtained by the present invention are explained asfollows.

The first unit is connected to one end of the optical composite cable.Then other optical composite cables are connected in sequence to theother end of the optical composite cable by cascade connection, and theoptical composite cables are extended. The second unit is connected tothe other end of the extended optical composite cables, and the detectorof the present invention detects the transmission performance of thoseconnected optical composite cables. By carrying out these processesevery time the optical composite cable is connected, it becomes possibleto quickly know which one of the optical composite cables is broken.

Also, when the optical composite cables are connected to each other inused state, the first unit is connected to the end of one opticalcomposite cable at the side the TV camera is connected, the second unitis connected to the connector of the optical composite cable which isinstalled at the farthest side from the first unit, and thentransmission performance of the optical composite cable between each endis measured. Next, the optical composite cable is taken off at thefarthest side from the first unit, the second unit is connected to theconnector of the next optical composite cable in the transmission linewhich is installed at the farthest side from the first unit, and thentransmission performance of that optical composite cable between eachend is measured. By carrying out those processes toward the first unitrepeatedly, it is detected which one of the optical composite cables hastrouble.

Accordingly, only one of the second unit and the first unit connected tothe optical composite cables may be shifted. That enables to detecttroubles of transmission line using the optical composite cablesextremely easier when the cables are installed in the field.

As a result, troubles in a transmission circuit comprising opticalcomposite cables which is employed to connect TV cameras to telecastfrom outdoor can be detected more easily.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features, and many of the attendant advantages ofthe present invention will be readily appreciated as the same becomesbetter understood with reference to the following detailed descriptionof the preferred embodiments when considered in connection with theaccompanying drawings, in which:

FIG. 1 is an electric block diagram showing structure of a detectordetecting transmission performance of optical composite cable accordingto an embodiment of the present invention;

FIGS. 2A and 2B are views showing mechanical structure of a measure unitof the detector according to the embodiment of the present invention;and

FIGS. 3A and 3B are views showing mechanical structure of a loopbackunit of the detector according to the embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will next be described based onconcrete examples. The scope of the present invention, however, is notlimited to the embodiment described below.

A detector detecting transmission performance of optical composite cablecomprises a loopback unit 10 as a first unit and a measure unit 40 as asecond unit. The loopback unit 10 comprises an optical loop part, or aloop fiber 11 which connects an end ‘a’ of a first optical fiber 31 andan end ‘b’ of a second optical fiber 32. The loopback unit 10 comprisesa short-circuit part, or a short-circuit wiring 12, which short-circuitsthe ends c and d of a pair of signal lines 33 and 34, the ends e and fof a pair of signal lines 35 and 36, and the end g of a shield line 37.

An optical composite cable 30 comprises the first optical fiber 31, thesecond optical fiber 32, the pair of signal lines 33 and 34, the pair ofsignal lines 35 and 36, and the shield line 37.

The measure unit 40 comprises a light-emitting device 41 which outputspulse optical signal to the first optical fiber 31, and alight-receiving device 42 which receives pulse optical signal reflectedby the loopback unit 10. The light-emitting device 41 is driven by adriver 43. A controller 50 comprises MPU and outputs control signal tothe driver 43. Optical signal received by the light-receiving device 42is amplified by an amplifier 44, the amplitude value is converted by aD/A converter 45 into digital signal and is stored by a memory 46.According to the command from the controller 50, a selector 47 selectsone pair of lines from 5 electric lines: a pair of signal lines 33 and34; a pair of signal lines 35 and 36; the signal line 33 and the shieldline 37; the signal line 34 and the shield line 37; the signal line 35and the shield line 37; or the signal line 36 and the shield line 37.The selector 47 supplies constant amount of electric current to one ofthe selected lines through an electric line port 49, and outputsterminal voltage of the other line to the D/A converter 48. The D/Aconverter 48 converts the terminal voltage into digital value and storesthe value in the memory 46.

The controller 50 checks quantity of transmission loss of the opticalfiber and breaking of the electric lines according to the valuememorized in the memory 46. The result is shown by a liquid crystaldisplay unit through a display-control circuit 51. The controller 50receives command to start measurement or command to measure calibrationfrom an operator 53. A housing of the measure unit 40 has structureshown in FIGS. 2A and 2B, and a housing of the loopback unit 10 hasstructure shown in FIGS. 3A and 3B.

A housing 70 formed in a rectangular column shape comprises each deviceshown in a block view of FIG. 1. On the front plane of the housing 70, aliquid crystal display screen 72 constructing the display unit 52 andpush-button switches 74 constructing the operator 53 are installed.These push-button switches 74 allows the housing 70 to send command tostart measurement or command to start calibration. Also, a connector 71which is connected to a connector in the optical composite cable isformed at one end of the housing 70, and a dust cap 73 is disposed toprotect the connector 71.

As shown in FIGS. 3A and 3B, the loopback unit 10 comprises a housing 80formed in a rectangular column shape and a connector 81 which is formedat one end of the housing 80 and is connected to a connector of theoptical composite cable. And a dust cap 83 is disposed to protect theconnector 81.

Accordingly, the detector detecting transmission performance of opticalcomposite cable of the present invention has structure as explainedabove.

A transmission loss measuring part of the present detector comprises thecontroller 50, the driver 43, the light-emitting device 41, thelight-receiving device 42, the amplifier 44, the D/A converter 45, andthe memory 46. A resistivity measuring part of the present detectorcomprises a electric line port 49, a selector 47, a D/A converter 48, amemory 46, and a controller 50. A disconnection detecting part comprisesthe controller 50. And a display part comprises the display-controlcircuit 51 and he display unit 52.

Next, actions of the detector of the present invention are explainedhereinafter.

First, the measure unit 40 and the loopback unit 10 are connecteddirectly with each other through connectors 71 and 81, respectively. Andmeasurement is started by operating the push-button switch 74 of theoperator 53. Transmission loss X between ends of a pair of optical fiber31 and 32 and six resistivity values Y1 to Y6 in total, or resistivityY1 between ends of a pair of signal lines, resistivity Y2 between endsof a pair of power supply lines, resistivity Y3 between ends of onesignal line and the shield line, resistivity Y4 between ends of thesignal line and the shield line, resistivity Y5 between ends of onepower supply line and the shield line, and resistivity Y6 between endsof the other power supply line and the shield line, are measured andstored. Because the measure unit 40 and the loopback unit 10 areconnected directly with each other, there is no optical fiber, signalline, and power supply line between those units. The terms of thetransmission loss and the resistivity values described above is definedon the supposition that those optical fibers, signal lines and powersupply lines described above are existed.

Large value of transmission loss X represents soiled ferrule of theconnector, so it needs to be cleaned. When transmission loss X isnormal, the push-button switch 74 of the operator 53 is operated andthat value is stored as calibration value. After calibration isfinished, transmission loss displayed by the display unit 52 is 0 dB.Such calibration value can be maintained when power supply switch isoff.

Next, an optical composite cable is installed between the loopback unit10 and the measure unit 40 in order that its transmission performance ismeasured. By operating the push-button switch 74 of the operator 53,command to start measurement is given and transmission loss A betweenends of optical fibers and the six resistivities R1 to R6 between endsof electric lines are measured.

True transmission loss W between ends of optical fiber is calculated bya formula A-X and is displayed at the display unit 52. When transmissionloss W between ends of optical fiber is larger than the predeterminedthreshold Tw1, the display unit 52 displays sign “NG.” That is, thedisplay unit 52 shows sign of disconnection of optical fibers. Whentransmission loss W between ends of optical fiber is smaller thanthreshold Tw1 and larger than the predetermined threshold Tw2, which issmaller than threshold Tw1, the display unit 52 displays the signshowing that the ferrule of the connector is soiled.

True resistivities V1 to V6 between ends of electric lines arecalculated by a formula subtracting the six resistivities Y1 to Y6 frommeasured values R1 to R6, respectively. V1 represents resistivitybetween ends of signal lines and V2 represents resistivity between endsof power supply lines. And shield line resistivity S can be calculatedby the following formula:

When resistivity between ends of power supply lines is normal,S=(V5+V6−V2)/2  (1)

When resistivity between ends of power supply lines is abnormal, or whenpower supply lines are disconnected,S=(V3+V4−V1)/2  (2)

Here V1 represents true resistivity between ends of signal lines, V2represents true resistivity between ends of power supply lines, V3represents true resistivity between ends of one signal line and theshield line, V4 represents true resistivity between ends of the othersignal line and the shield line, V5 represents true resistivity betweenends of one power supply line and the shield line, and V6 representstrue resistivity between lines of the other power supply line and theshield line.

When each of these values is larger than a certain threshold, it isjudged that disconnection occurs. The liquid crystal display unit showsdisconnection status of the signal lines, the power supply lines, andthe shield line.

In case that the power supply lines are normal, resistivity of theshield line is calculated by using the formula (1) when resistivitybetween ends of power supply lines is normal. Because the power supplylines are thicker and have smaller resistivity than the signal lines,extremely precise value of resistivity of the shield line can beobtained by using the formula (1).

In the present invention, transmission loss between ends of opticalfibers and respective resistivities between ends of each electric linesare determined by employing average value of 4 times of measurementseach measured at 10 msec, respectively.

INDUSTRIAL AVAILABLENESS

The present invention can be employed as a tester for an opticalcomposite cable, or a composite cable comprising optical fiber andelectric line, which connects a TV camera and a relay car to telecastfrom outdoor. The tester of the present invention enables to detectdisconnection or status of transmission of the optical composite cableas an extremely light portable device.

The present invention has been described in detail with reference to theabove embodiments serving as most practical and appropriate examples.However, the present invention is not limited to these embodiments, andappropriate modifications and applications can be made without deviatingfrom the scope of the present invention.

While the present invention has been described with reference to theabove embodiments as the most practical and optimum ones, the presentinvention is not limited thereto, but may be modified as appropriatewithout departing from the spirit of the invention.

The present invention comprises all the contents in the priorityclaiming Japanese patent application No. 2005-86710.

1. A detector detecting transmission performance of optical compositecable which comprises optical fibers and electric lines, comprising: afirst unit which is connected to a connector formed at one end of saidoptical composite cable and comprises a optical loop part connecting afirst optical fiber and a second optical fiber and a short-circuit partwhich short-circuits plural electric lines in said optical compositecable; and a second unit comprising a transmission loss measuring part,which is connected to a connector formed at the other end of saidoptical composite cable and measures transmission loss between ends ofsaid first optical fiber and said second optical fiber returned by saidoptical loop unit, a resistivity measuring part, which measuresresistivity between ends of electric lines returned by saidshort-circuit part, a disconnection detecting part, which detectsconnection or disconnection of electric lines by using measuredresistivity, and a display part, which displays the result oftransmission loss measured by said transmission loss measuring part andconnection or disconnection detected by said disconnection detectingpart.
 2. A detector detecting transmission performance of opticalcomposite cable according to claim 1, wherein said electric linescomprise a pair of signal lines and a pair of power supply lines and ashield line, said resistivity measuring part measures resistivitybetween ends of a pair of signal lines returned from said short-circuitpart, resistivity between ends of a pair of power supply lines returnedfrom the short-circuit part, and each resistivity between each ends ofeach signal line and said shield line returned from the short-circuitpart, each resistivity between each end of each power supply line andsaid shield line returned from the short-circuit part, and saiddisconnection detecting part detects each disconnection status of thesignal line, the electric line, and the shield line according to thosemeasurement results.
 3. A detector detecting transmission performance ofoptical composite cable according to claim 1, wherein said transmissionloss measuring part outputs a pulse optical signal to the first opticalfiber and receives the pulse optical signal from the second opticalfiber synchronizing with sending said pulse optical signal.
 4. Adetector detecting transmission performance of optical composite cableaccording to claim 2, wherein said transmission loss measuring partoutputs a pulse optical signal to the first optical fiber and receivesthe pulse optical signal from the second optical fiber synchronizingwith sending said pulse optical signal.